In recent years, a digital still camera using a high-pixel-density image sensor has been commercialized. In general, the digital still camera using a high-pixel-density image sensor adopts a driving method as the operation mode of the image sensor during EVF display or moving image sensing. In this driving method, signal lines other than those necessary for display on a liquid-crystal display device are thinned out to increase the finder rate.
A high-resolution digital still camera has been strongly required to sense a still image as instantaneously as a silver halide camera. To meet this demand, the time from when the release switch is pressed until image sensing must be short sufficiently. Especially, because AF requires only a short time until focusing, a variety of inventions associated with the phase difference AF scheme have been proposed.
Japanese Patent Laid-Open No. 2000-156823 discloses a technique associated with an AF scheme. This technique arranges photoelectric conversion elements for phase difference AF on the image sensor and uses a signal output from the image sensor in order to perform phase difference AF without any mechanical phase difference detection structure.
Japanese Patent Laid-Open No. 2003-198925 discloses a technique of switching lines to be read out between the AF time and the image generation time when the lines of the image sensor are thinned out and read out in EVF display or moving image sensing in an image sensing apparatus in which the image sensor includes photoelectric conversion elements for phase difference AF.
However, as for an image sensor having lines including photoelectric conversion elements for phase difference AF and lines including no photoelectric conversion elements, the techniques disclosed in Japanese Patent Laid-Open Nos. 2000-156823 and 2003-198925 read out lines including no photoelectric conversion elements for phase difference AF in EVF display or moving image sensing. These techniques read out lines including photoelectric conversion elements for phase difference AF in AF. This approach cannot cope with an image sensor in which photoelectric conversion elements for phase difference AF are arranged in all lines.
In addition, the techniques disclosed in Japanese Patent Laid-Open No. 2000-156823 and 2003-198925 read out lines including photoelectric conversion elements for phase difference AF from the image sensor again in AF, and use only the AF data. For this reason, as described in Japanese Patent Laid-Open No. 2003-198925, an image one frame before is displayed or recorded again in EVF display or moving image sensing in AF, resulting in the generation of an uncomfortable moving image such as that which freezes halfway.